Auxiliary Electrode Connection Stability in Display Devices
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Solution Overview
Problem
The existing display devices face issues with unstable electrical connections between the auxiliary electrode and the upper electrode due to the under-cut region, leading to resistance variations and luminance unevenness.
Innovation Solution
The display device incorporates a lower passivation layer with a first penetrating hole exposing the auxiliary electrode and an over-coat layer with a second penetrating hole, where the second penetrating hole has a reverse taper on one side and a positive taper on the other, ensuring a stable electrical connection by preventing continuous under-cut regions and maintaining the thickness of the upper electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an under-cut region is formed by a lower passivation layer and an over-coat layer to prevent light-emitting layer deposition on the auxiliary electrode, then the light-emitting layer can be prevented from depositing on the auxiliary electrode, but the upper electrode may be partially broken or have thin thickness in the under-cut region, resulting in unstable electrical connection and resistance variation
Solution Approach 1:
A connection electrode is introduced as an intermediary component between the auxiliary electrode and the upper electrode. This connection electrode is positioned in the under-cut region and provides a reliable electrical connection path, mediating the connection while preventing direct contact between the upper electrode and auxiliary electrode through the problematic under-cut region, thus ensuring both deposition control and electrical stability
Solution Approach 2:
The electrical connection path is segmented into multiple components: the auxiliary electrode, the connection electrode, and the upper electrode. By dividing the connection function across these separate elements, the design allows the upper electrode to maintain its integrity while still achieving electrical connection to the auxiliary electrode through the connection electrode that spans the under-cut region
2Illumination intensity
If the upper electrode is formed with relatively thin thickness to improve display performance, then the display performance is enhanced, but the electrical connection between the auxiliary electrode and upper electrode becomes unstable due to resistance variation in the under-cut region
Solution Approach 1:
The connection electrode serves as a mediator that carries the electrical connection function separately from the upper electrode. This allows the upper electrode to be formed with thin thickness for optimal display performance while the connection electrode provides a robust electrical connection path through the under-cut region, isolating the thin upper electrode from resistance variations
Data Source
Figure 1A~1B
Figure 2A
Figure 2B~2C
AI summary
A display device including an auxiliary electrode in order to prevent the luminance unevenness is provided. In the display device, an under-cut region may be formed by a first penetrating hole of a lower passivation layer and a second penetrating hole of an over-coat layer in order to connect an upper electrode to the auxiliary electrode. The second penetrating hole of the over-coat layer may be disposed to be offset from the first penetrating hole of the lower passivation layer, so that the under-cut region may be partially broken in an edge of the auxiliary electrode. Thus, the display device may improve the reliability of the electrical connection between the auxiliary electrode and the upper electrode.